AT&T Wireless has begun selling Research In Motion's BlackBerry device with a color screen, helping the Canadian company to expand its core business audience.

Redmond, Wash.-based AT&T Wireless announced Wednesday that it is now offering RIM's BlackBerry 7210, which is a combination cell phone and messaging device with a color screen. U.S. subscribers to AT&T's cellular GSM/GPRS (Global System for Mobile Communications/General Packet Radio Service) network will be able to make calls, send e-mail messages and surf the Web using the $450 device and paying $40 per month for service. Optional voice plans for the device will start at $20.

AT&T Wireless had 21.49 million subscribers in the United States as of June 30, according to the carrier.

The BlackBerry 7210 is a dual-band GSM/GPRS device. On Monday, RIM partner T-Mobile USA announced it is selling a tri-band product from the 7200 series, the 7230, which also features a color screen. The carrier is selling the device for $400 and $30 per month for service.

The two announcements emphasize that Waterloo, Ontario-based RIM is pushing to expand its audience by targeting individual professionals, such as lawyers and doctors. It traditionally aims its products at businesses that buy devices in batches in tandem with RIM's server software.

To reach the new audience, the company is adding features to its devices that are designed make it more competitive and attractive to individuals.

"Color is now the standard, and there will be very few monochrome-screened devices being sold by year-end," hedge fund analyst Brian Blair of Bluewater Captial said in an instant message.

RIM is embroiled in a series of lawsuits with Xerox and Good Technology. In addition, a judge ruled earlier this month in favor of holding company NTP, awarding it monetary damages and fees from its patent-infringement case against RIM. The judge also granted an injunction against RIM selling its products and services in the United States, but stayed the order pending an appeal by RIM.